During steel pipe manufacturing by the Mannesmann process, a piercer works a billet where the outer surface of the billet is in contact with guide shoes. Therefore, if the lubrication between the outer surface of the billet and the guide shoes is inadequate, sticking will damage the guide shoes themselves, and the outer surface of the pierced crude pipe (hereinafter referred to as “hollow shell”) will suffer damages due to sticking which are called shoe marks.
There are two types of guide shoes, fixed plate type and rotary disk type. In either case, it is very important to maintain a good supply of lubrication to prevent such sticking. Thus, there are some proposals regarding the method of lubrication, as follows.
In Patent Document 1, a piercing-rolling method is disclosed, which comprises applying a mixed coating composition that is comprised of a metal oxide, a powder-based anti-sticking material and a binder.
In Patent Document 2, a lubricant for hot rolling of stainless steel species is disclosed, which is comprised of an iron oxide powder, a water-soluble acrylic polymer and a surfactant.
In Patent Document 3, a lubricant for hot working is disclosed, which is comprised of iron oxide, sodium silicate, starch species and xanthan gum.
However, in the case of piercing a hard-workable material such as a 13% Cr steel species, the lubricants disclosed in these documents cannot reduce the friction between the guide shoes and the hollow shell to a sufficient extent, and therefore cannot prevent the occurrence of damages due to sticking to a satisfactory extent.
[Patent Document 1] JP-A-S60-21111
[Patent Document 2] JP-A-H07-126684
[Patent Document 3] JP-A-H11-35967